1. Field of the Invention
The present invention relates to a controlled fiber-optic switch for selectably connecting or disconnecting the ends of first and second optical fibers by lateral displacement of the first fiber's end between a "connect" position which is in opposition to the second fiber's end, and a second position in which both fibers are disconnected. The invention further relates to a method of operation of a fiber-optic switch.
2. Prior Art
In communication and computer systems using fiber-optic network, there is a need of occasionally interconnecting or connecting and disconnecting signal lines which may be represented by single optical fibers each. One of several possible applications could be for Local Area Networks (LAN) configuration.
Several switching devices for establishing selectable connections are already proposed. Fibers which are used for this application have a small cross-section of typically 125 .mu.m with a core diameter of less than 10 .mu.m for single mode, and less than 65 .mu.m for multimode case. Therefore, switching can be accomplished by very small relative diplacement of selected fibers' ends against others. For safe operation it is necessary to keep the fibers' ends in good relative axial alignment if they are in the `connect` position. In order to allow easy mechanical displacement operation, the opposite ends of `connected` fibers--according to the state of the art--are kept in a certain distance of typically a few .mu.m. It was reported (P. G. Hale et. al.: Mechanical optical-fiber switch. Electronic Letters IEE Jul. 22, 1976, p. 148) that with this small distance the line's transmission losses are rather low. However, with extreme high bit-rates and longer distance applications which are now coming up, for example in the range of 1 to 2 GBit/s, monomode fibers must be used as optical tranmission medium, requiring special lasers as light sources which have a high resonance gain and which do not generate side modes. Useful lasers (e.g. index guided lasers or distributed feedback (DFB) lasers) are increasingly sensitive to back-reflected light which interferes with the electro-optical laser cavity operation. In an attemp to further reduce back-reflection and transmission losses between fiber ends, it was proposed to apply a clear liquid between opposite fiber ends. Liquids, however, are highly unwanted in field operation because most known optical liquids do not have sufficient optical stability over several years, especially when they become exposed to high temperatures or frequent alterations in ambient conditions.